1) You can dash after the elevator has the "go down" button on with everyone on it.
2) You can dash while dead (The failed revive that makes you hit revive again, but dash works as you "fail" to get up, leaving your body to literally skip across fire and stuff).
If you dash when you actiavte the elevator sequence thing, you become invincible. However, if you dash then you lose your invincibility. This could cause problems.